Marker projectiles for use in training or war games are well known and examples of such projectiles are disclosed in U.S. Pat. No. 4,686,905, GB 2 284 252, GB 1 263 522, U.S. Pat. No. 3,528,662, U.S. Pat. No. 4,128,059 and U.S. Pat. No. 3,782,286.
Most of the aforementioned patents disclose projectiles in which a marker substance is held within a frangible casing or enclosure which ruptures upon impact with a target. A problem with projectiles such as bullets that are intended to break upon impact is that sometimes they fail to break. Moreover, because of the high impact required to break the frangible casing or enclosure, the projectiles can often cause injury upon impact with a person. A further problem is that the frangible casings or enclosures can sometimes break in a gun during the gun's reloading cycle.
Some of the aforementioned problems are addressed in GB 2 284 252 which discloses a projectile comprising a hollow casing having a perforated nose portion, a piston disposed within the casing, and a marking substance disposed forwardly of the piston. The piston is movable forwardly under force applied to it by gas used to discharge the projectile thereby compressing the marking substance and expelling it through the nose portion which thus becomes coated with the marking substance. Upon impact with a target, the marking substance is transferred to the target to mark the target.
However, a problem with projectiles, such as those disclosed in GB 2 284 252, in which the nose portion of the projectile is coated with a marking substance even before the projectile has left the gun barrel, is that the marking substance is dispersed by the rotation imparted to the projectile by the rifling in the gun barrel. Thus, the centrifugal force imparted by the spinning bullet causes the marking substance to move radially outwardly and consequently it can foul the barrel of the gun. A build up of marking substance, or its thermal decomposition products, in the gun barrel over time will inevitably have an adverse effect on the working of the gun. This problem is greatly exacerbated with bullets designed for use in high velocity rifles such as the NATO and US 5.56 mm calibre rifles where the rifling in the barrel must be such as to impart a very high spin rate to the bullet in order to ensure a stable trajectory. Even with relatively low velocity training ammunition, the high spin rates imparted by the rifling in high velocity rifles are still sufficient to cause the marking substance to disperse in the manner described above.
A still further problem with the marker projectile of GB 2 284 252 and other known marker projectiles is that they are unsuitable for small calibre barrels such as the current NATO and US 5.56 mm calibre self loading rifle barrels. This is not only because of the problem of radial dispersion of the marking substance referred to above, but also because the complexity of the bullet poses considerable manufacturing difficulties with smaller calibre bullets.
International Patent Application number PCT/GB00/00241 discloses a marker projectile which goes some way to overcoming the aforementioned technical problems. The marker projectile in that patent specification is characterised by a marker substance being disposed in a hollow chamber with a front opening. An expelling member is positioned behind the marker substance with respect to the front opening. The configuration of the projectile is such that, on impact with a target, the momentum of the expelling member relative to the hollow body carries the expelling member forwardly towards the impacted target so as to expel the marking substance in a low impact manner. These marker projectiles are distinguished from known projectiles such as those disclosed in GB 2 284 252 where a piston within the projectile is driven forwardly by the propellant gases in the cartridge or gun to expel the marker substance. In the projectiles described in PCT/GB001/00241, the expelling member is insulated from the propellant gases; in other words, the propellant gases do not act on the expelling member to force it forwardly to cause expulsion of the marking substance.
The family of patents derived from the Applicant's own earlier international patent application number PCT/GB03/02344 discloses a solution to improve the spread of a marker substance expelled by a non-lethal, low impact projectile of the type described in PCT/GB00/00241. PCT/GB03/02344 describes a non-lethal marker projectile comprising a hollow body having an opening at the front; a marker substance disposed within the hollow body; and an expelling member within the hollow body behind the marking substance; the hollow body and expelling member being configured such that upon impact of the projectile with a target, the momentum of the expelling member relative to the hollow body carries the expelling member forwardly to expel the marking substance through the opening and characterised by a separator extending at least partly over the front opening, the separator defining two or more spaces through which the marker substance may pass when expelled through the opening.
The present invention seeks to provide a marker projectile which provides further improved marking over a wide range of temperatures.